# 5.3: Bulk Density

Bulk density is the dry mass of a soil divided by the total soil volume. The bulk density value for soil is calculated using the formula:

Bulk Density = mass (g) oven dry soil / total soil volume (cm3)

$D_b = \frac{ODwt}{V_t} \nonumber$

Some typical values for the bulk density of soils having different textures along with the corresponding porosity percentages are given In Table 1.

Table 1. Typical bulk density, porosity, and pore size distribution of several soils.

For a particular soil, the bulk density may vary due to compaction or loosening as a result of tillage operations, or other forms of soil disturbance. Variation of bulk density means the porosity will also change. Some soils (surface of forest soils, Histosols, and soils derived from volcanic ash) have very low bulk density values (often less than 1.0 gram/cm3), due to high porosity.